Heart failure is usually a chronic, long term condition, but may occur suddenly. It may affect the left heart, the right heart, or both sides of the heart. Heart failure may be considered as a cumulative consequence of all injuries and/or stress to the heart over a person's life and the prevalence of heart failure increases constantly. For example, it is estimated that nearly 5 million people in the U.S.A. suffer from heart failure and about 400.000 new cases are diagnosed every year. The prevalence of heart failure approximately doubles with each decade of life. One of the most important means of treating heart failure is cardiac resynchronization therapy, CRT. Although CRT is a very effective way of treating heart failure in most patients there is a large percentage for which the CRT has no apparent effect at all. Different estimates of the size of the so called group “non-responders” exist, but it is generally believed to be in the vicinity of 25% of all patients provided with a CRT device. However, there are numbers reported to be as high as 33% (depending mostly on the definition of CRT response which may vary greatly).
A common method for adapting the CRT (the timing cycles) for non-responders is so called echo-based optimization, which may include M-mode, 2D, 3D and TDI. Echo-based optimization of the timing cycles is often time-consuming and may range from 30 minutes to two hours depending on the scope of the evaluation. Furthermore, echo-based optimization is heavily dependent of the operator, who interprets the displayed echo signals, for accuracy and consistency. Accordingly, there is a need for more reliable, fast, and accurate methods for CRT timing optimization and for patient customized CRT timing optimization.
Device based CRT optimization is likely to be one of the most potent tools in improving CRT efficiency and more specifically fighting non-responders. St. Jude Medical's QuickOpt™ Timing Cycle Optimization is an algorithm that provides IEGM (Intracardiac Electrogram) based AV (Atrial-Ventricular) timing optimization in CRT and ICD (Implantable Cardioverter-Defibrillator) systems and VV (Ventricular-Ventricular) timing optimization in CRT devices in a simple and swift way. QuickOpt™ Timing Cycle Optimization is based on the hypothesis that the point of time for the closure of the Mitral valve can be estimated by measuring the interatrial conduction time (P-wave duration), that the onset of isovolumetric contraction can be measured using the peak of the R-wave and that interventricular conduction delays can be measured by evaluating simultaneous RV (Right Ventricular) and LV (Left Ventricular) IEGMs and measuring the time between the peaks of the R-waves. The goal is to characterize interatrial conduction patterns so that preload is maximized and ventricular pacing does not occur until after full closure of the mitral valve and to characterize intrinsic and paced interventricular conduction patterns so that pacing stimuli and the resultant LV and RV conduction (paced wave fronts) meet at the ventricular septum. Accordingly, QuickOpt™ Timing Cycle Optimization electrically characterizes the conduction properties of the heart to calculate optimal paced and sensed AV delay, i.e. the time interval between a paced atrial event and the ventricular impulse and a sensed atrial event and the ventricular impulse, respectively, and/or VV delay. QuickOpt™ Timing Cycle Optimization has been clinically proven to correlate with the more time-consuming echo-based methods and may be used for patients carrying CRT and dual-chamber devices at implant or follow up. QuickOpt™ Timing Cycle Optimization is an appealing optimization method since it does not require systematic measurements of a number of different AV and VV delays, which makes it very fast and simple. There are other IEGM based optimization methods among which QuickOpt™ Timing Cycle Optimization is one such method.
Despite the evident advantages of IEGM based optimization methods, such as e.g. QuickOpt™ Timing Cycle Optimization, there is an opinion within the medical community, for example, among physicians that results, e.g. timing cycles, based on input data more directly reflecting the mechanical functioning of the heart may be even more accurate and reliable.
Thus, there is still a need within the art for further improved method and devices for optimizing AV and VV delays.